VENNEGUES , Philippe

Les nitrures d'éléments III et les alliages à base de ZnO, semi-conducteurs à large bande interdite étudiés au CRHEA, cristallisent dans la structure hexagonale wurtzite. Cette structure a la particularité d'être une structure polaire et les polarisations internes ont donc une forte influence sur les propriétés des hétérostructures à base de...

The absolute epitaxial relationships between III-nitride films and R-plane sapphire are investigated using convergent beam electron diffraction. The resulting relationships are found to be[1−100]III-N‖‖[11−20]sapphire and [0001]III-N‖‖[−1101]sapphire, respectively. The O–Al bonds in the sapphire surface are antiparallel to the N-III bonds in...

International audience

International audience

In a polycrystalline γ-γ′ nickel-based superalloy, γ′ precipitates with a close-to-twin orientation relationship to their surrounding matrix (named T-type precipitates) are found in recrystallized grains located near specific unrecrystallized grains (named recovered grains). This type of γ/γ′ interface has not been reported in literature...

International audience

We report on the impact of structural defects on mid-infrared intersubband (ISB) properties of GaN/(Al, Ga)N heterostructures grown by ammonia molecular beam epitaxy (NH 3 MBE). Twenty-period GaN/(Al, Ga)N multi-quantum-well (MQW) heterostructures are grown on co-loaded a-plane freestanding GaN substrates and heteroepitaxial a-plane GaN on...

This paper demonstrates the existence of large γ' precipitates (several micrometres in diameter) that are coherent with their surrounding matrix grain in a commercial γ–γ' nickel-based superalloy. The use of combined energy dispersive X-ray spectrometry and electron backscattered diffraction (EBSD) analyses allowed for revealing that surprising...

In this contribution, we performed the growth of a 3C-SiC/Si/3C-SiC layer stack on a Si(001) substrate by means of chemical vapor deposition. We show that, by tuning the growth conditions, the 3C-SiC epilayer can be grown along either the [111] direction or the [110] direction. The key parameter for the growth of the desired 3C-SiC orientation...

DNP are observed in fibres when alkaline-earth elements (Mg, Ca and Sr) are incorporated. Mean size of the DNP, deduced from SEM pictures, depends on the composition... This last composition leads to a low loss fibre... From EDX measurements, we have observed that alkaline-earth elements and erbium ions are located inside or very close to the...

No description

GaN-Al0.5NGa0.5N quantum dots deposited on (11-22) planes have been grown by combining Molecular Beam Epitaxy and Metal Organic Vapour Phase Epitaxy. This combination is interesting for realization of ultraviolet operation light emitting diodes, lasers andsingle photon sources,… (1,3) The growth of dots was achieved by MBE using ammonia as...

International audience

Structural and morphological characterization of a Si(110) film heteroepitaxied on 3C-SiC(001)/Si(001) on-axis template by chemical vapor deposition has been performed. An antiphase domain (APD) free 3C-SiC layer was used showing a roughness limited to 1 nm. This leads to a smooth Si film with a roughness of only 3 nm for a film thickness of...

International audience

International audience

We exhibit both experimentally and theoretically a novel growth mode for the epi-taxy of AlGaN quantum dots (QD), where they are eventually produced without their usual surrounding wetting layer. If the generic evolution of QD is ruled by the elastic relaxation and capillary effects, evaporation occurs here on a time scale similar to that of...

Particles in the core of optical fibers are widely studied to tailor or to improve optical properties. The analysis of nanoparticles embedded in silica-based optical fiber allowed new observations of the evolution of amorphous particles during fiber drawing. Even at the nanoscale, competition between viscous stresses and surface tension on the...

International audience

National audience

International audience

International audience

International audience

International audience

National audience